1. Field of the Disclosure
The present invention relates generally to methods and apparatus for handling pipes and other tubular members during drilling and/or workover operations of a well. More specifically, the present invention relates to an impact absorbing “diving board,” or access platform, of a “fingerboard,” or pipe racking assembly, used for staging pipes and other tubular members adjacent to a drilling rig in a substantially vertical orientation while the drilling and/or workover operations are being performed.
2. Description of the Related Art
Drilling masts are vertical structures that are commonly used to support a drill string while a well is being drilled. Drilling masts usually have a relatively compact, rectangular footprint, as opposed to a derrick structure, which typically has a steep pyramidal shape. The rectangular shape of the typical drilling mast also offers relatively good overall stiffness, which allows the mast to be lowered to a horizontal position. The compact, rectangular shape of the drilling mast structure therefore facilitates transportation of the drilling rig over surface roads, many times without the need for obtaining special shipping permits, and thereby making drilling masts very common on portable land-based drilling rigs. FIG. 1a shows an elevation view of an illustrative portable land-based drilling rig 1 having a drilling mast 2.
During typical drilling operations, a string of drill pipe—shown as reference number 6 in FIG. 1a—which may have a drill bit mounted on the lower end of the drill string 6, may be suspended from a traveling block 3 and top drive assembly 4 in the drilling mast 2. As may be required for some specific drilling operation, the top drive 4 assembly imparts a rotational force to the drill string 6, thereby turning the drill bit and advancing the depth of the drilled wellbore. As the depth of the wellbore increases, additional lengths of drill pipe are added to the drill string 6 at the surface.
Due to the relatively compact footprint that may be associated with drilling mast structures, there may be very limited space available for storing the drill pipe and other tubular members adjacent to the drilling mast 2. Therefore, in many cases, the drill pipe may be vertically staged in a specially designed structural assembly—sometimes referred to as a racking board or fingerboard 5—that is attached to the drilling mast 2, as shown in FIG. 1a. The fingerboard 5 is specifically designed to facilitate the vertical arrangement of the various sections of drill pipe during the drilling operations. While the fingerboard 5 is commonly attached directly to the drilling mast 2, it may be positioned many feet—for example, 75 feet or more—above the drilling rig floor 7, depending on the length of the various sections of staged drill pipe. FIGS. 1b and 1c show a close-up elevation view and a plan view, respectively, of the position of the fingerboard 5 relative to the drilling mast 2, the traveling block 3, the top drive assembly 4, and the drill string 6.
“Tripping” is a term of art used in drilling operations that generally refers to acts of either adding multiple joints of drill pipe to, or removing multiple joints of drill pipe from, a drilled wellbore. Oftentimes during the drilling operations, tripping operations may be performed wherein the drill string 6 is pulled from the wellbore in order to change the drill bit, or to run various other types of equipment, such as testing equipment and the like, into the wellbore on the end of the drill string 6. When tripping drill pipe out of the wellbore, the traveling block 3 and top drive assembly 4 may be raised until a stand of drill pipe (i.e., generally multiple connected sections, or joints, of drill pipe) extends above the drilling rig floor. In most cases, a stand of drill pipe may comprise two or three joints of drill pipe, with the most common pipe stand configuration being three joints of drill pipe, totaling approximately 90 feet in length. Thereafter, slips are placed between the string of drill pipe and the drilling rig floor in order to suspend the drill string 6 in and above the wellbore from a point beneath the bottom threaded joint of the stand of drill pipe that is to be removed from the drill string. In this position, the drill string 6 extends above the drilling rig floor 7, and the upper end, or box end, of the string is positioned above the plane of the fingerboard 5, which, as noted previously, may be located 75 feet or more above the drilling rig floor 7.
Once the drill string 6 has been suspended with its box end positioned above the fingerboard 5, the threaded connection between the stand of drill pipe and the remainder of the drill string 6 is then unthreaded, and the lower end, or pin end, of the stand is guided away from the remainder of the drill string 6 and wellbore and placed on a support pad—sometimes referred to as a setback—on the drilling rig floor 7. Next, the box end of the stand of drill pipe is removed from the traveling block 3/top drive assembly 4 and the stand is typically manually guided by drilling rig personnel to the fingerboard 5, where it is staged between a set of racking fingers 8 (see FIG. 1c) in a substantially vertical orientation. In this position, the box end of the removed stand of drill pipe remains a few feet above the plane 5p of the fingerboard 5. The top drive assembly 4 is then lowered to the box end of the suspended drill string by the traveling block 3 and coupled to the drill string 6. Thereafter, the drill string 6 is again lifted to a position where the box end is positioned above the plane 5p of the fingerboard 5, and the process is repeated until all of the sections of pipe—e.g., in three joint stands—are supported at their respective pin ends on the setback, with their respective box ends being constrained between pairs of racking fingers 8 on the fingerboard 5. When a new drill bit or other type of tool is being run into the well, the above-described tripping process is reversed and repeated, as the pin end of each stand of drill pipe is threaded into the box end of the drill string 6, and the drill string 6 is lowered into the well until the drill bit or other tool reaches a desired depth in the wellbore.
The movement of stands of drill pipe from the top drive assembly 4 to the racking fingers 8 of the fingerboard 5 is often manually effectuated by rig personnel, who may pull and/or push the drill pipe to its proper staging location. Furthermore, it is generally well understood that such movements of large sections of drill pipe may involve a variety of difficulties that, if not properly addressed by rig personnel involved in the work, may be hazardous to those personnel working above the rig floor and near the fingerboard. For example, the job of maneuvering the stand of drill pipe to its proper staging location may entail such activities as reaching out from the area of the fingerboard 5 to where the stand of drill pipe is located above the centerline 9 (see FIG. 1c) of the well in order to disconnect the box end of the stand from (and/or to connect the box end to) the top drive assembly 4. Furthermore, the work may include moving the upper end of each stand of drill pipe from its location at or near the centerline 9 of the well over to and into the racking fingers 8 of the fingerboard 5, and vice versa. To enable rig personnel to perform these operations safely, the fingerboard 5 may include access platforms 10 adjacent to and surrounding the racking fingers 8. The fingerboard 5 may also sometimes include an additional access platform 11, sometimes referred to as a diving board 11, in order to facilitate easier access to the traveling block 3, the top drive assembly 4, and/or the drill string 6. As shown in FIG. 1c, the diving board 11 may in some instances run down the center of the fingerboard 5—i.e., between rows of racking fingers 8—and extend away from the fingerboard 5 towards the centerline 9 of the well. Additionally, the diving board 11 may included hinged extension section 11a, which may be folded out for closer access to the centerline 9 of the well, or folded back to provide more clearance between the traveling block 3/top drive assembly 4 and the diving board 11 during some rig operations.
Recently, various efforts have been undertaken to automate at least some aspects of the operations that are commonly used for running drill pipe into and out of the wellbore—i.e., tripping the drill string—so as to avoid at least some of the constant interaction of rig personnel with the various pieces of equipment and materials that are in motion during drilling operations, such as the drill string 6, the traveling block 3, and/or the top drive assembly 4. For example, some complex automatic systems have been developed to perform the pipe handling steps of moving the stands of drill pipe between the pipehandler assembly 4a (see FIG. 1b)—which is a key pipe handling component of the top drive assembly 4—positioned at the centerline 9 of the well and the fingerboard 5. Additionally, some of these exemplary automatic systems include devices and equipment that move the stands of drill pipe around the fingerboard 5 and into (or out of) the racking fingers 8. In order to facilitate movement of the stands of drill pipe in and around the fingerboard 5, some of these exemplary automatic systems may utilize the structure of the centrally-located access platform—i.e., the diving board 11—to support the additional devices and/or equipment necessary to perform these pipe handling activities. Depending on the overall design of the automatic pipe handling system, the structural integrity of the diving board 11 may, in some cases, be significantly enhanced, thereby resulting in a much larger, heavier, and more complex assembly.
During the above described pipe tripping operations, it is very common for the traveling block 3 to be raised and/or lowered very quickly, which can help to speed up these otherwise time-consuming—and costly—drill pipe handling operations. However, due to the speed of these activities, the time that rig personnel may have to react to anomalies in the overall operations—such as errors, mistakes, or oversights by other personnel, or to otherwise unanticipated equipment failures—may be significantly reduced, thereby increasing the likelihood that accidents may occur. By way of example, in some cases, the top drive assembly 4 may not be properly oriented or aligned during some phases of the operations, which may cause some portions of the top drive assembly 4 to project farther from the centerline 9 of the well than would otherwise be anticipated. In other cases, the links of the pipehandler assembly 4a may not be properly oriented or fully retracted, a situation which may also cause the top drive assembly 4 to project farther from the well centerline 9 than normal. Under such circumstances, it may be possible for the top drive assembly 4 to strike the diving board 11 as the top drive assembly 4 is being raised and/or lowered by the traveling block 3. The likelihood of such a strike may be further exacerbated in those cases where the diving board 11 includes a hinged extension section 11a, and when that hinged extension section 11a may be folded out for closer access.
The force that may be imparted to the diving board 11 by the moving mass of the traveling block 3, the top drive assembly 4, and the drill string 6—which will depend on the speed at which those elements are moving—may result in considerable damage to the structure of the diving board 11, the fingerboard 5, and even the top drive assembly 4. Furthermore, if proper safety procedures are not observed during drilling activities, there may be a substantial risk of injury to rig personnel during such occurrences. It should be further noted that any type of damage to the diving board 11, the fingerboard 5, and/or the top drive assembly 4 may result in significant and costly down-time for the rig while the necessary repairs are affected. Moreover, when the fingerboard 5 and diving board 11 incorporate devices and equipment associated with the types of complex automatic pipe handling systems discussed previously, the cost and down-time for repairing any damage may be substantially greater than that associated with relatively simple structural repairs.
Accordingly, there is a need to develop and implement new designs for the diving board structures of drilling rig fingerboards to address the issue of damage that may occur when the diving board may be inadvertently struck by drilling equipment during drilling operations. The present disclosure relates to methods and devices that may avoid, or at least reduce, the effects of one or more of the problems identified above.